Many so-called "experts" advise re-applying stone sealers on an annual (or more frequent) basis - they are in all likelihood just trying to get you to buy more of their expensive sealer. Borelli Marble & Granite doesn't advise any preset "calendar" for re-sealing, and over-application of sealer can build up over time and cause a haze on the surface of your countertops. The frequency for re-sealing depends on the type of stone installed and the amount of use that the countertops see. An easy "rule of thumb" is to closely monitor the area around the sink. If you begin notice water that does not bead up or soaks into the stone within 10-15 minutes, then it's probably time to re-seal. Applying a sealer is easy, you can apply a liberal amount of sealer in the evening before going to bed and just let it penetrate and cure overnight.